Image handling and display in X-ray mammography and tomosynthesis

ABSTRACT

A method and system for acquiring, processing, storing, and displaying x-ray mammograms Mp tomosynthesis images Tr representative of breast slices, and x-ray tomosynthesis projection images Tp taken at different angles to a breast, where the Tr images are reconstructed from Tp images.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.15/282,596, filed Sep. 30, 2016, now U.S. Pat. No. 10,108,329, which isa continuation application of U.S. patent application Ser. No.14/742,040, filed Jun. 17, 2015, now U.S. Pat. No. 9,460,508, which is acontinuation application of U.S. patent application Ser. No. 12/344,121,filed Dec. 24, 2008, now U.S. Pat. No. 9,095,306, which is acontinuation application of U.S. patent application Ser. No. 11/271,050,filed Nov. 11, 2005, now U.S. Pat. No. 7,577,282, which is acontinuation-in-part of earlier-filed application Ser. Nos. 10/305,480and 10/723,486, filed respectively on Nov. 27, 2002 and Nov. 26, 2003,and claims the benefit of provisional applications Nos. 60/628,516 and60/631,296 filed respectively on Nov. 15 and 26, 2004, and incorporatesherein by reference the entire contents of each of said earlier-filedpatent applications. To the extent appropriate, priority is claimed toeach of said earlier-filed patent applications.

FIELD

This patent specification pertains to x-ray mammography andtomosynthesis, and more specifically to techniques and equipment foracquiring, processing, storing and displaying mammograms, tomosynthesisprojection images, and tomosynthesis reconstructed images.

BACKGROUND AND SUMMARY

Mammography has long been used to screen for breast cancer and otherabnormalities. Traditionally, mammograms were formed on X-ray film, butmore recently flat panel digital imagers have been introduced thatacquire a mammogram in digital form and thereby facilitate analysis andstorage. Further, X-ray tomosynthesis of the breast has been proposedrecently, as discussed in the earlier-filed applications identifiedabove, and clinical testing has been carried out. The assignee of thispatent specification, Hologic, Inc., has demonstrated at trade shows inthis country a fused, multimode mammography/tomosynthesis system thattakes either or both types of images, and either while the breastremains immobilized or in different compressions of the breast.

Tomosynthesis as used in the systems and methods disclosed in thispatent specification typically involves acquiring a plurality oftomosynthesis projection images Tp at respective angles relative to thebreast, and reconstructing therefrom a plurality of tomosynthesisreconstructed images Tr representative of breast slices. Proper displaytechniques are desirable to make the presentation of Tp and/or Tr imagesmore effective and efficient for review by health professionals. Whentomosynthesis projection images Tp are acquired along with conventional2D mammograms Mp, improved display methods are desirable that facilitatethe display of both types of images. Effective display approaches alsoare desirable when tomosynthesis images Tp or Tr that are acquired atone time need to be compared to mammograms Mp or to tomosynthesis imagesTp or Tr acquired at a different time. Another display issue relates toComputer Aided Detection (CAD) methods that use computer analysis ofimages to identify locations and possibly other characteristics ofsuspected abnormalities. CAD marks currently are placed on mammogramimages Mp, but it may be useful to place them at the appropriatelocation on Tr or Tp images. Conversely, it may be desirable to obtainCAD marks by processing Tp and/or Tr images, and place them atappropriate locations on Mp images. Here the notation Mp refers to aconventional mammogram, which is a two-dimensional projection image of abreast; the term Mp encompasses both a digital image as acquired by aflat panel detector or another imaging device and the image afterconventional processing to prepare it for display to a healthprofessional or for storage, e.g. in the PACS system of a hospital oranother institution. Tp refers to an image that is similarlytwo-dimensional but is taken at a respective tomosynthesis angle betweenthe breast and the origin of the imaging X-rays (typically the focalspot of an X-ray tube), and also encompasses the image as acquired aswell as the image after being processed for display or for some otheruse. Tr refers to an image that is reconstructed from images Tp, forexample in the manner described in said earlier-filed patentapplications, and represents a slice of the breast as it would appear ina projection X-ray image of that slice, and also encompasses informationsufficient to describe such a slice image. The images Mp, Tp and Trtypically are in digital form before being displayed, and are defined byinformation identifying properties of each pixel in a two-dimensionalarray of pixels. The pixel values typically relate to respectivemeasured or estimated or computed responses to X-rays of correspondingvolumes in the breast.

Yet another issue concerns the large storage requirements oftomosynthesis images Tp and/or Tr. Because the reconstructed datasetsfor Tr images are large, it may be better in some circumstances to storeunreconstructed projections Tp, which require less storage. Transmissiontimes to the storage device, and from the storage device to the displayworkstation, can thus be reduced. The Tp images in this case can bereconstructed to Tr images just prior to viewing. Further, it may bedesirable that images viewed on a workstation are the same or at leastcomparable to images viewed on a different workstation, or the same orat least comparable to images previously viewed of the same dataset,even if the software and/or hardware of the acquisition or workstation,or acquisition system, has changed.

Yet another issue concerns the processing time required to reconstructtomosynthesis images Tr. Because of relatively long reconstructiontimes, one possible approach is to perform reconstructions at anacquisition console, and send the already-reconstructed images todisplay workstations. This can allow a greater reading throughput ifthere are several acquisition systems that are all pushing images to oneor more display workstations. The system can be designed so that it canhandle M acquisition consoles sending their images to all N displayworkstations.

In one non-limiting example disclosed in this patent specification,acquisition and display of x-ray images starts with acquiring x-raymammography image data representative of projection mammography imagesMp of patients' breasts and x-ray tomosynthesis image datarepresentative of projection images Tp taken at different angles of atleast a source of imaging x-rays relative to the patients' breasts(e.g., different angles of the focal spot in an X-ray tube relative animmobilized breast). This acquisition can be performed by a single unit,using a single X-ray tube and a single flat panel digital imager or someother imaging device, configured to selectively acquire one or both ofthe mammography and tomosynthesis image data, in the same compression ofa patient's breast or in different compressions. The disclosed systemand method use at least a subset of the acquired Tp images to formreconstructed tomosynthesis images Tr representative of slices of thebreasts that have selected orientations and thicknesses. The system andmethod display at least a selected subcombination of the Mp, Tr and Tpimages, preferably for concurrent viewing and preferably while showing,at or near the displayed images, respective labeling symbols identifyingthem as Mp, Tr or Tp images.

The method and system can further generate or otherwise obtain computeraided detection (CAD) marks for suspected abnormalities in said Mpimages, and can display said marks at corresponding locations on Trimages associated, e.g. by orientation, with respective Mp images. Inaddition to location information, the CAD marks can provide informationregarding, for example, the type of suspected abnormality and/or aconfidence level that the marks points to an actual abnormality. CADmarks that are initially generated from or are otherwise related to someof the Tr, Tp or Mp images can be displayed at images from which theywere not generated or with which they were not initially associated, atcorresponding or at least related locations. Tp images can be storedtogether with version information indicative of at least one of anacquisition configuration used to acquire them and a reconstructionconfiguration used to reconstruct Tr images from said Tp images, tothereby enable later reconstruction of Tr images that match thosereconstructed originally. Alternatively, or in addition, Tp images canbe stored together with version information related to when they wereacquired and can be later reconstructed into Tr images using areconstruction configuration that matches the version information. Areconstruction configuration can be provided that has at least twodifferent versions of reconstruction software, so that Tr images can bereconstructed using a version of the reconstruction software thatmatches the version information of the Tp images or earlier Tr images.Tr images can be reconstructed from only a subset of the acquired Tpimages, which in an extreme case means reconstruction from a single Tpimage to yield an equivalent of the Tp image. Tr images representativeof at least two breast slices that differ in thickness can be formed,for example using MIP (Maximum Intensity Projection) methods or asumming method that may or may not use different weighting of the summedpixel data. The display can be toggled between Tr images representativeof breast slices having different thicknesses, wherein the slices may ormay not overlap in space. Through computer-processing, the volume of alesion can be computed and displayed from information contained in theMp, Tr and/or Tp images. The display can show concurrently Tr imagesreconstructed from a current acquisition of Tp images and at least oneMp image obtained from a previous acquisition involving a differentbreast compression. The concurrent display can be on the same ordifferent monitors, and can include at least Mp and Tr images, or atleast Mp and Tp, images, or at least Tr and Tp images, or all threetypes of images, and can instead or additionally include 3D imagesformed from some or all of the acquired X-ray data, image data and/orfrom Mp, Tr and/or Tp images. Information indicative of status ofloading Tr images for display can be shown as a part of the display.Different images can be displayed at different pixel sizes or fields ofview or, alternatively, they can be selectively equalized by pixel sizeor field of view by selected types of interpolation or extrapolation,for example by up-converting to a smaller pixel size and thus a higherconverted pixel count or by down-converting to a larger pixel size andthus a lower pixel count.

The concurrent display of Mp and Tr images can include displayingnon-numeric indications of respective levels of displayed Tr imagesrelative to Mp images, for example in the form of cross-lines on a barrelated to displayed Mp images, wherein the height of the bar may relateto the thickness of the compressed breast, and/or non-numericindications of respective thicknesses of breast slices represented bydisplayed Tr images, for example in the form of cross-bars of respectivethickness on a bar related to Mp images. Instead, or in addition,numerical indications can be provided and displayed of the position of aslice image Tr relative to a breast imaged in an image Mp, and/or thethickness of the slice. Mp and Tr images can be shown overlaid on eachother, and toggling can be allowed to switch between the image that isvisible at the time. In addition, other image display effects can beprovided, such as, without limitation, fade-in/fade-out and blending twoor more images at respective weighting, as commonly used inpost-production of television images and in known image processingsoftware such as Photoshop from Adobe. Tr images can be displayed inciné mode, with selective control over the speed of changing from oneimage to another and/or the order of images for display relative to anorder in which they were reconstructed. At least two sets of Tr images,e.g. Tr images reconstructed from different acquisitions of Tp images,can be shown concurrently and scrolled through in synchronism. Aselection of initial or default display modes can be provided relatingto the order, speed, slice thickness and/or other parameters of displayof images, and user selection among those modes can be allowed.Information regarding image data acquisition, storage, reconstructionand/or other parameters can be selectively displayed. Tr images can beprinted in an N×M format (where N and M are positive integers), andprinting of images displayed concurrently on one or more monitors inWISIWIG format can be allowed. Compression of Mp, Tp and/or Tr imagesand/or of image data can be selectively carried out prior to storage.The compression can be lossless, or it can be lossy to a selecteddegree. Reconstruction of Tr images can be selectively carried out fromcompressed Tp images. Window/level controls can be provided for at leastselected ones of the displayed images, and the controls can be set bythe user, or automatically, to control the window width and/or thewindow level of only one, or only selected ones, or all of the displayedimages. Image regions can be magnified for display, and the window/levelcontrols automatically applied to the magnified regions. The Tr, or theTp, or both the Tr and Tp images, can be stored in PACS storage. The Tpimages can be acquired by using coarser binning in a direction ofrelative motion between the source of imaging x-rays and a breast duringimage acquisition. Alternatively, such binning can be done after the Tpimages are acquired, to thereby reduce storage and further processingrequirements. The Mp and Tp images that are concurrently displayed canbe acquired from the same breast of a patient while the breast remainsimmobilized under compression that can remain the same or change betweenthe acquisition of Mp images and Tp images. Alternatively, the Mp and Tpimages can come from different acquisitions at different times ordifferent breast compressions. Image data for Tp images acquired at twoor more acquisition units can be supplied to and reconstructed into Trimages at a single reconstruction unit, from which one or more datadisplay units can acquire Tr images for display, or image data for Tpimages can be stored as such and only reconstructed into Tr imagesimmediately prior to display thereof.

An additional or alternative display approach uses the Tp and/or Trimages in stereoscopic display. For example, when any two Tp imagestaken at different angles to the breast are displayed concurrently andviewed such that each is seen by a different eye of the observer, depthinformation is visualized. Similarly, when any two Tr images arereconstructed such that their image planes are at an angle to eachother, depth information can also be perceived.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating flow of data through a systemwhere reconstruction of tomosynthesis slice images Tr occurs after (or,alternatively, before) storage of acquired tomosynthesis projectionimages Tp.

FIG. 2 is a block diagram illustrating flow of data where thereconstruction of images Tr occurs before storage.

FIG. 3 illustrates an example where four units acquiring Tp images feeda single unit that reconstructs Tr images.

FIG. 4 illustrates an example where each of four units acquiring Tpimages has its own unit for reconstructing Tr images.

FIG. 5 illustrates an example of displaying Tr (or Tp) images andmammogram images Mp at separate areas of a single screen or on differentscreens.

FIG. 6 illustrates an example where an Mp image and a Tr image may beshown at the same or substantially same area on a screen, with anexample of a non-numeric indication of a thickness and position in thebreast of a breast slice represented by a Tr image.

FIG. 7 illustrates a concurrent display of Tr and Mp images, at separateareas on a screen or as combined images.

FIG. 8 illustrates a display of Mp/Tr images with CAD marks and anon-numeric indication of Tr images in which CAD marks exist.

FIG. 9 illustrates stereoscopic display of Tp images.

FIG. 10 illustrates stereoscopic display of Tr images.

FIG. 11 is a block diagram illustrating major elements of amammography/tomosynthesis system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In describing preferred embodiments illustrated in the drawings,specific terminology is employed for the sake of clarity. However, thedisclosure of this patent specification is not intended to be limited tothe specific terminology so selected and it is to be understood thateach specific element includes all technical equivalents that operate ina similar manner.

Illustrates flow of data in one example of a system disclosed in thispatent specification. An image data acquisition system 1 acquirestomosynthesis and/or mammography image data for Tp and/or Mp images ofpatients' breasts, and can take the form of and use the acquisitionmethods of any of the systems disclosed in said earlier-filed patentapplications. Following acquisition, the data describing projectionimages Tp are sent to storage device 2, which can include a PictureArchiving and Communication System (PACS) storage, for example of thetype commonly used in hospitals and other healthcare facilities,preferably a DICOM-compliant PACS. When images are needed for display 4,the data for Mp and/or Tp images are sent, from either acquisitionsystem 1 or from storage device 2, to a computer system 3 configured asa reconstruction engine that can perform tomosynthesis reconstructioninto images Tr representing breast slices of selected thickness and atselected orientations, as disclosed in said earlier-filed patentapplications. The reconstructed slice images Tr are then sent to adisplay system 4 so that they can be viewed. If the reconstructionengine 3 is connected to display 4 via a fast link, then large datasetscan be transmitted quickly.

Over time, there will likely be improvements to the acquisition systemsand to the display systems, which may result in hardware and softwareupgrades and changes to reconstruction algorithms. This can createissues in viewing images taken previously. It may be important to beable to recall from storage and reconstruct an image that looksidentical (or is at least comparable) to the way it looked when it wasreconstructed and displayed in the past. Consider the example where animprovement in reconstruction algorithms improves image quality so as toallow detection of a cancerous lesion in an image where it was notvisible using a previous version of the reconstruction algorithm and thethen existing standard of care. While it could be useful to see olderimages processed with the newer algorithms, it may also be important toallow the re-display of images as they were viewed during an originaldiagnosis. One way to accomplish this in accordance with the disclosurein this patent specification is to put a version number or some otherinformation in the data for Tp images, which identifies the softwareand/or hardware versions of the image data acquisition and/or Tr imagereconstruction system at the time of acquisition. During reconstructionat a later time, the reconstruction engine reads this version number orother similar information and reconstructs using the appropriatealgorithm. Thus, system upgrades can maintain a library of olderalgorithms and/or hardware so as to be able to reconstruct using theproper technique.

An alternative design is illustrated in FIG. 2. In this example, thereconstructions at unit 3 occur near or at the acquisition station 1,and it is the reconstructions Tr that are sent to storage system 2 anddisplay devices 4. One advantage of the configuration of FIG. 2 is inthe way it handles acquisition upgrades—if a new hardware/softwareversion has a modified reconstruction algorithm, then all Tr imagesreconstructed from Tp image data taken after the upgrade willautomatically reflect this new algorithm, and Tr images reconstructedfrom Tp image data taken prior to the upgrade will have beenreconstructed with the older version and properly stored as such. Theimages stored on a PACS will be the same as they were viewed by theradiologist or other health professional during the diagnosis or otherinitial review. Another advantage of the system of FIG. 2 is the reducedsystem reconstruction burden compared to the system in, where thereconstruction engine is just prior to the display. If there aremultiple acquisition systems, for example four systems, that are allpushing images to the display, then the reconstruction engine in willneed to reconstruct images at 4 times the rate of a reconstructionengine in a system having only one acquisition system, for the sametotal patient throughput.

An example of such a four-acquisition station system using the design ofis illustrated in. An example of a four-acquisition station system usingthe design of is illustrated in, and this system can reconstruct moreimages in a given amount of time due to the increased number ofreconstruction engines.

The question of which system design will place a greater burden on thePACS storage of an institution will depend upon the sizes of the rawprojections Tp and of the reconstructed images Tr. In general, if theraw projections Tp are smaller than the reconstructed images Tr, itmight be desirable to save in PACS the raw or preliminarily processeddata for Tp images and reconstruct the final Tr images on demand fordisplay or other use. In all cases it may be desirable to keep both ofthese sizes as small as possible.

One way to reduce the size of an original dataset for a Tp image is tobin the projection Tp data to as large a pixel size as practical withoutreducing clinical efficacy of the final Tp or Tr images. It can beparticularly useful to bin the pixel data asymmetrically, with a coarserbin in the direction of motion of a source of the imaging x-raysrelative to the breast being imaged and a finer bin in the orthogonaldirection, as described in at least one of said earlier-filed patentapplications. The binning can be done as a part of the X-ray dataacquisition process, in the course of reading out measurement data froma flat panel digital imager. Alternatively, it can be done after initialdata acquisition. Compression of the projections using lossless or lossycompression algorithms can also serve to reduce the image size. Thereare different ways to reduce the size of the reconstructed datasets forTr images, and this can be particularly important if the reconstructionsare being saved in PACS, and if they are being transmitted through thehospital or other facility network. Data compression is one way toreduce dataset size. Another is to make the reconstructed pixel sizes aslarge as practical consistent with the clinical imaging task. It isbelieved that, as one non-limiting example, a pixel size of 140microns×140 microns for the reconstructed slices is reasonable for manyif not most viewing purposes. The display system can interpolate orextrapolate to a finer pixel size for display, and this can be usefulwhen it is desired to confirm the pixel size of another image, such as adigital mammogram taken at a finer resolution than 140 microns. It isalso faster to reconstruct into a coarser pixel size and then performdisplay interpolation or extrapolation to a finer pixel size, and doingso may not affect clinical efficacy as long as the reconstructed pixelsize is adequately fine.

The same tomosynthesis acquisition system can be capable of acquiringeither mammograms Mp or tomosynthesis images Tp (reconstructed intotomosynthesis images Tr), or both, as described in said earlier-filedapplications. Thus, a display system preferably should be able todisplay both Mp and Tr (and/or Tp) images concurrently or sequentially.Similarly, the display system preferably should be able to display thecurrent images as well as additional images taken at other times. Thetomosynthesis acquisition can acquire mammograms and tomosynthesisimages Tp in a single compression, as described in said earlier-filedapplications. In such a case, because the breast geometry is essentiallyunchanged between the two image types, a location in an Mp or Tr imagecan be related to the same breast location in the other image. If thecorrelative geometry exists, the two image types can be overlaid on topof each other, and the user can toggle back and forth between whichimage type is visible at a given time. Thus, in general, the display cansimultaneously or sequentially display mammograms and tomosynthesisimages Tr (and/or Tp) from the current and previous studies.

Methods of identifying which image corresponds to which image type indisplays of Mp, Tr and/or Tp images are desirable. One example of such amethod is illustrated in FIG. 5. An icon is used to identify an imagetype. In this non-limiting example, the symbol M on the left imageindicates that it is a mammogram. The symbol T on the right imageindicates that it is a tomosynthesis slice image Tr. Similarly, a symbolTp (not shown) can be used to indicate that the displayed image is atomosynthesis projection image Tp, and the symbol 3D (also not shown)can be used to indicate that an image on the display is a 3D image.Other symbols serving a similar purpose can be used instead of, or inaddition, to those identified above.

The system described as a non-limiting example in this patentspecification is capable of receiving and displaying selectively thetomosynthesis projection images Tp, the tomosynthesis reconstructionimages Tr, and/or the mammogram images Mp. It can receive images storeduncompressed, losslessly compressed, and lossyly compressed. It can alsoinclude algorithms to decompress images sent in compressed format. Thesystem has software to perform reconstruction of tomosynthesis imagedata for images Tp into images Tr. Further, it can include software togenerate 3D display images from the tomosynthesis reconstructed imagesTr using standard known methods such as MIP (Maximum IntensityProjection), summing, and/or weighted summing algorithms.

Referring to the tomosynthesis image Tr displayed on the right of FIG.5, a slider bar indicates the height of the displayed slice, in thisexample above the breast platform, although the height could be relatedto other references instead. In this case the height is approximately 5cm. The height of a Tr slice that is displayed can be changed using astandard computer interface, such as a keyboard or mouse or mouse wheelor trackball. When the height changes, the slider bar updates by movingup or down to accurately reflect the displayed slice. Another method ofdisplay is an overlay method, where the mammogram Mp and the tomographicslice image(s) Tr are stacked one on top of another. This is illustratedin. The symbol TM in this non-limiting example means that the display isan overlay of at least one tomosynthesis image Tr plus a mammogram imageMp. The visible image, that is the image type on top, can be changedfrom Tr to Mp and vice versa easily, such as toggling back and forthusing a keyboard or another interface device. The image type that isvisible can be identified by changing the symbols such as bolding orunderlining the top one. For example, if the image Tr was on top, thesymbol could be TM, while if the image Mp was on top the symbol could beTM. As noted above, the top image can be made partly transparent, andother techniques such as fading one image into the other can be used.FIG. 6 further illustrates another display method. In addition to theslice height of a Tr image, the slice thickness can be adjusted anddisplayed, preferably non-numerically. Alternatively, the displayedslice height and/or thickness can be displayed in a numeric format.Typically, the breast slices represented by Tr images are thin, on theorder of 0.5-3 mm, and will not show objects that are far from the givenslice. If it is desired to view objects seen from a thicker slice, onecan perform reconstructions to generate Tr images of synthesized thickerslices, such as 5, 10, 15 or 20 mm or more, or two or more Tr images canbe blended into a single Tr image representing a thicker slice. Theblending can be with the same or different weighting of the original Trimages.

The control of the Tr slice image that should be displayed can behandled in a number of different ways. The user can click or drag theslider bar to the desired slice height, and the display would follow.Alternatively, the height could be selected using keyboard commands,mouse wheels or trackballs, or other such computer selection tools. TheTr slice image can be played in ciné mode, with the speed and directioncontrollable by the user. Tomosynthesis projection images Tp can also bedisplayed in cine mode.

If two or more sets of tomosynthesis images are displayed concurrently,for example Tr images from the same breast taken at different times, orTr images of the two breasts taken at the same time, these two sets ofimages can be simultaneously displayed in cine mode. The ciné displayscan be synchronized, so that if these two datasets represent the samebreast, the ciné display of both will traverse through each breastdataset at the same rate.

The display of the slice image Tr has, in addition to the display of theslice height, a graphical method of displaying the corresponding slicethickness. The width of the cross-bar shown in illustrates the slicethickness.

These Tr images for thicker slices can be derived in several ways. Oneway is to sum together a number of the adjacent thinner Tr slice images.Another is to calculate a maximum intensity projection through theadjacent slices. Yet another way to change the slice thickness is toreconstruct the dataset using a subset of the projections Tp. If oneuses fewer projections, this is equivalent to an acquisition over ashallower angle and consequently the reconstructed images Tr have agreater depth of field and thus represent thicker slices. For example,if only one projection is used to reconstruct, this represents atomosynthesis acquisition over a 0° angular scan and the depth of fieldis infinite, i.e. the reconstructions are 2D, as in an Mp image of thesame breast.

In the most general case, the display screens will contain a mixture ofmammogram Mp, tomosynthesis Tr and/or Tp, and combination (Mp+Tp/Tr)images. One example of this is illustrated in FIG. 7. It shows a 4-viewexamination being compared to a prior 4-view exam, where different viewsof different breasts are either Mp, Tr/Tp, or combination displays. Thesoftware allows the selection of one or more image planes, for use inimage processing, or to change window/level or to change slice height,etc. The selected image planes are indicated in some way; in thisnon-limiting example the selected plane is outlined with a dotted line.These sets of images can be on one monitor, or on multiple monitors orother displays.

When more than one image is displayed, it is convenient to have theimages all be displayed at the same pixel spacing, using knowninterpolation or extrapolation method applied to digital images. Thisfacilitates image comparison. As an example, if the prior mammogram wasacquired on a system using 100 micron pixel spacing, but the currentmammogram was acquired on a system using 70 micron pixel spacing, thedisplay will map the images so the pixel spacings are identical. Thispixel spacing is also true for Mp and Tr/Tp images. In a preferredembodiment, the Mp and Tr/Tp images are displayed at the same pixelsize. This is especially useful in performing overlaid image display,with the Mp and Tr/Tp images on top of each other. Thus, an object in aTr image will appear at the same place as in the corresponding Mp image.If the two images are not at the same pixel size, toggling between themmay show a distracting change due to the difference in pixel size.Matching the pixel spacings for all images on the display is only onepossibility. A capability to change the pixel spacings of any image orsets of images, such as would occur when one zoomed a region of abreast, can also be included.

Zooming can be done on any of the images on the display. In particular,in a combo overlay display mode, the zoomed area will zoom both the Mpand the Tr slice images as they are toggled. In other words, no matterwhat image type is displayed, it will be zoomed. Window/level can beindependently, or jointly, applied to any combination of images on thedisplay. In particular, for the Tr images the window/level can beapplied to just the single displayed Tr slice image, or all the Tr sliceimages. If there is a magnified region of an image, window/level can beselectively applied just to the magnified region or to the entire image.

A compressed breast is frequently about 50 mm thick, and if thereconstructed slice separation is 1 mm then the examination will consistof 50 slices. The time it takes to load this study into display might besignificant. Because of this, it can be useful for the display toindicate the status of the display if the image is currently beingloaded. This can take the form of a message such as “image loading” oran icon indicating the same, or information providing more detailregarding loading status such as, without limitation, remaining time forcompleted display.

The sequence of displaying Tr images can be controlled to select eitherthe first, last, or middle, or some other Tr slice image, as the initialslice to display. This control also defines the starting slice thicknessto display.

CAD algorithms are commonly used to analyze mammograms. CAD can also beapplied to Tr and/or Tr images. It can be useful to display CAD marksthat are derived from or are otherwise associated with the Tr/Tp images,at the appropriate locations on the Mp images. For example, when a Trslice image is displayed that contains one or more CAD marks, the x, ylocation of the CAD mark on the Tr slice image is used to compute thecorresponding x, y location on the Mp image that represents the samebreast location. The mark can then be placed on one or both of the Mpand Tr images at the same locations. Similarly, it can be useful todisplay CAD marks that are derived from or are otherwise associated withthe Mp images on the appropriate locations on the Tr slice images. Forexample, the x, y location from the Mp CAD mark is used to compute thecorresponding x, y location on the Tr slice image that represents thesame breast location, and the mark is placed on the Tr slice.

One method of displaying CAD information is illustrated in. Slicelocations where there are CAD marks are indicated. In this example, theyare indicated though the use of arrows positioned at the slice heightswhere the marks are. In this non-limiting example, there were CAD marksat heights 1 and 3 cm, and the currently displayed slice is at 5 cm.

Another display method for use with Tr images that have Tr CAD data isto restrict the display of Tr slice images that do not have CAD marks onthem. For example, if only Tr slice images 10 and 20 had CAD marks, thenonly those two slice images would be displayed. This allows the speedupof image review, because there can be 50 or more Tr slices that need tobe displayed. The image display could jump from one CAD-marked sliceimage Tr to another quickly. There can also be an override method sothat all the slice images Tr could be reviewed if desired.

In addition to CAD information display, the unit can display patientdemographic and acquisition information relevant to the acquisition andreconstruction of Tp/Tr images.

There also are different methods of printing Tr/Tp images. Because thereare many slice images Tr, it may not be desirable to print out eachindividual slice image. In this case, the system can support printing ofthe Tr images in an N×M film layout format. In addition, printing can beallowed in a screen capture WYSIWYG (What You See Is What You Get)format.

A common method of reviewing digital mammography and tomosynthesisimages Mp, Tp, and Tr is by using one or more monitors, and looking atthe images in an essentially monoscopic mode—the same image is viewed byboth of the viewer's eyes. Researchers have proposed using stereoviewing systems, whereby different images are presented to the left andright eyes. This method of viewing is known as stereoscopic, and canoffer distance or depth cues similarly to what is normally seen by humaneyes in regular vision tasks. Stereoscopic viewing offers potentialbenefits in viewing radiological images, because relative spatialrelationships between objects in the body might be more apparent. Onesuch stereoscopic system, for use in medical displays, is proposed inU.S. Pat. No. 6,031,565 issued on Feb. 29, 2000 and involves taking tworadiographic images of a body from different angles. The and the displayof these two images provides depth information.

Tomosynthesis images offer new opportunities for improved stereoscopicviewing, at least in part because it provides a richer dataset than justa stereo pair to be displayed, it provides many possible combination ofimage pairs, and provides for scrolling through different displayed setsof images.

One method of display using pairs of images from the tomographicprojection dataset Tp is illustrates in FIG. 9. Any two pairs ofprojections Tp may provide stereo visualization, and by displayingdynamically sets of these pairs of projections, one will get both astereoscopic view and one which dynamically moves around the body thatwas imaged. For example, consider that 8 projections Tp were taken as apart of a tomosynthesis acquisition: Tp[1], Tp[2], . . . Tp[21]. Thefirst pair to be stereo viewed could be Tp[1] and Tp[3], the second pairTp[2] and Tp[4], the third pair Tp[3] and Tp[5] and so on to Tp[6] andTp[8]. Alternatively pairs could be adjacent pairs such as Tp[1[ andTp[2] or separated by three projections Tp[1] and Tp[4], etc. Theoptimal spacing between the two projections in the displayed stereo pairis dependent upon the imaging geometry and angular separation betweensuccessive projections Tp[i] and Tp[i+1]. It is known that only certainangular differences between stereo pairs give good stereo visualizationto humans, and the selection of appropriate pairs of images Tp for aparticular acquisition setting can be determined through convenientexperimentation.

Another method of display uses a variant of the reconstructed dataset Trand is illustrated in FIG. 10. In this embodiment, one reconstructs twodifferent datasets Tr′ and Tr″, both reconstructed from some or all ofthe original projections Tp. When performing reconstruction, one choosesthe geometry of reconstruction and it is possible to reconstruct thesetwo datasets into images Tr that differ in their view of the body by aselected angular separation, e.g. a few degrees, thus mimicking theapparent viewing of the body that the human eye would see, if it hadx-ray vision. Each dataset Tr′ and Tr″ consist of sets of crosssectional slices. If one displays, using the stereo viewer, the sameslice from Tr′ and Tr″, one in the left eye and the other in the righteye, one would get a stereo perspective of that slice. One could displaydifferent slice pairs in depth succession in the breast to get a dynamicstereo view through the body. As seen in FIG. 9, an object 3000 isreconstructed with cross-sectional slices Tr′ and Tr″ perpendicular totwo different axes 3001 and 3002. The slice pairs that are displayed tothe left and right eye are Tr′[i] (3003) and Tr″[i] (3004). The anglebetween 3001 and 3002 is such that viewing the pairs Tr′ and Tr″ gives astereoscopic visualization. Unlike the proposal in said U.S. Pat. No.6,031,565, FIG. 9 illustrates a stereo view of a thin cross-sectionalslice through the body, and a scroll through such sections, while thepatent proposes displaying stereo pairs of projection radiographsthrough the entire body.

FIG. 11 illustrates an overall mammography/tomography system in whichthe preferred but non-limiting examples discussed above can beimplemented. The Figure illustrates in block diagram form an x-ray dataacquisition unit 100 that includes an x-ray source 110 imaging a breast112 supported on a breast platform 114. An x-ray imager 116 such as aflat panel x-ray imager commercially available from the assignee of thispatent specification generates projection image data that can be amammogram Mp or a tomosynthesis projection image Tp. X-ray source 110 ismounted for movement around breast platform 114 so that images Tp can betaken at different angles. X-ray imager 116 can be stationary or it canalso move relative to breast platform 114, preferable in synchronismwith movement of x-ray source 110. Elements 110 and 116 communicate withx-ray data acquisition control 118 that controls operations in a mannerknown from said earlier-filed patent specifications. X-ray image datafrom imager 116 is delivered to processing and image reconstruction unit120, where the data is processed as known from said earlier-filed patentapplication into Tp and Tr image data, possibly stored, and prepared fordisplay at image display unit 122 as disclosed in the variousembodiments described above.

The examples described above are only illustrative and that otherexamples also are encompassed within the scope of the appended claims.It should also be clear that, as noted above, techniques from knownimage processing and display methods such as post-production of TVimages and picture manipulation by software such as Photoshop fromAdobe, can be used to implement details of the processes describedabove. The above specific embodiments are illustrative, and manyvariations can be introduced on these embodiments without departing fromthe spirit of the disclosure or from the scope of the appended claims.For example, elements and/or features of different illustrativeembodiments may be combined with each other and/or substituted for eachother within the scope of this disclosure and appended claims.

The invention claimed is:
 1. A method of acquiring and displaying x-rayimages comprising: acquiring x-ray tomosynthesis image Tp datarepresentative of projection images taken at different angles of anorigin or imaging x-rays relative to a compressed breast, from anacquisition unit configured to selectively acquire the tomosynthesisimage Tp data; reconstructing at least a subset of the acquiredtomosynthesis image Tp data into reconstructed tomosynthesis image Trdata representative of images of slices of the compressed breast thathave selected orientations and thicknesses; and applying computer aideddetection (CAD) algorithms to at least one of the acquired tomosynthesisimage Tp data and the reconstructed tomosynthesis image Tr data todetect a suspected abnormality in the breast.
 2. The method of claim 1,further comprising: generating at least one of a tomosynthesisprojection image from the Tp data and a tomosynthesis reconstructedimage from the Tr data; and displaying, in the at least one of thetomosynthesis projection image and the tomosynthesis reconstructedimage, a CAD mark indicative of the suspected abnormality.
 3. The methodof claim 1, further comprising: acquiring x-ray mammography image Mpdata representative of a projection mammography image of the compressedbreast; and identifying a location in the Mp data corresponding to thesuspected abnormality.
 4. The method of claim 3, further comprising:generating a mammography projection image from the Mp data; anddisplaying, in the mammography projection image, a CAD mark at thelocation.
 5. The method of claim 1, further comprising: generating aplurality of tomosynthesis reconstructed images from the Tr data; andidentifying a subset of the plurality of tomosynthesis reconstructedimages, wherein the subset comprises tomosynthesis reconstructed imagesincluding the suspected abnormality; and displaying only the subset ofthe plurality of tomosynthesis reconstructed images.
 6. The method ofclaim 5, displaying sequentially the subset of the plurality oftomosynthesis reconstructed images.
 7. The method of claim 2, whereinthe CAD mark comprises information regarding at least one of a type ofthe suspected abnormality and a confidence level.
 8. The method of claim4, wherein the CAD mark comprises information regarding at least one ofa type of the suspected abnormality and a confidence level.
 9. Themethod of claim 6, further comprising displaying a slider bar foridentifying a height within the compressed breast corresponding to adisplayed image of the subset of the plurality of two reconstructedimages.
 10. The method of claim 9, further comprising identifying alocation on the slide bar corresponding to the CAD mark.
 11. A method ofacquiring and processing x-ray images, the method comprising: acquiringx-ray tomosynthesis image Tp data representative of projection imagestaken at different angles of an origin of imaging x-rays relative to acompressed breast, from an acquisition unit configured to selectivelyacquire the Tp data; reconstructing at least a subset of the acquired Tpdata into reconstructed tomosynthesis image Tr data; and generating aplurality of tomosynthesis reconstructed images from the Tr data,wherein a thickness of at least one of the plurality of tomosynthesisreconstructed images is adjustable.
 12. The method of claim 11, whereinat least two adjacent images of the plurality of tomosynthesisreconstructed images overlap in space.
 13. The method of claim 11,wherein a first image of the plurality of tomosynthesis reconstructedimages comprises a first thickness of the compressed breast, and whereina second image of the plurality of tomosynthesis reconstructed imagescomprises a second thickness different than the first thickness.
 14. Themethod of claim 11, further comprising displaying at least one of theplurality of tomosynthesis reconstructed images.
 15. The method of claim14, further comprising: displaying an information bar; and displaying aslice bar on the information bar, wherein a position of the slice bar onthe information bar corresponds to a first location within thecompressed breast of the first image of the plurality of tomosynthesisreconstructed images.
 16. The method of claim 15, wherein the slice barcomprises a thickness corresponding to a number of the displayedplurality of tomosynthesis reconstructed images.
 17. The method of claim15, wherein the slice bar comprises a thickness corresponding to athickness of a slice of the breast.
 18. The method of claim 11, furthercomprising generating a three-dimensional display image from the Tr datausing Maximum Intensity Projection.
 19. The method of claim 11, whereina first image of the plurality of tomosynthesis reconstructed images anda second image of the plurality of tomosynthesis reconstructed imagesare combined to form a third image.
 20. The method of claim 19, furthercomprising displaying the third image.